SMTP, which is short for Simple Mail Transfer Protocol, is the software that allows you to send out emails from your email addresses. Without this, you will not be able to employ email apps or webmail. Once you send an email, your SMTP server connects to a DNS server to learn exactly where emails for the recipient domain name are taken care of. Following that, it connects to the remote mail server and trades details. In case the recipient mail box is accessible, your server sends the message to the receiving POP/IMAP server and the latter delivers that message to the precise mailbox where the receiver can see it. If you wish to be able to send emails, it is best to make certain that the web hosting company has the service with their plans. Even if you use an online form that site visitors use to contact you, you'll still require an active SMTP server for your hosting account for the form to operate.